tcr20

Snow tires, 19" or 18" ? Is there a big reason to go with 18 or even 17 over 19 ?

ittazvic

For winter tires the highest sidewall is the best defense against potholes.

tcr20

from a snow, rain, ice traction perspective ?

MP4.2+6.0

Note w/ a W12 (or S8), you have to start w/ an 18" min. wheel diameter to clear the brakes, so I haven't thought about 17's other than for the A6.

Starting with the last one first--potholes--if that's your everyday winter environment, pretty easy choice to me: go to a smaller diameter wheel with a bigger sidewall tire to absorb those potholes and protect the rims. Note too as you go to the bigger ratio (sidewall) tires, the load rating goes up in the same width tire, also a good thing for a heavier vehicle like an A8. In my case, 90% of my miles in winter don't involve snow or really poor condition roads, so I put less priority here.

Once I get past that thinking, then I look at what is available in tire brands I am interested in. I also think through my starting tire circumference--27.6" on a 275/35 20 in my case. Below the 20" wheel size with a 275/35 tire in A8's IIRC you end up at 27" tire circumferences, includig an S8 with a 265/35 20. I prefer the bigger circumference, for appearance, very slight mileage diff, and to get the car that tiny bit higher rather than lower in winter. For me, I prefer a performance snow like a Dunlop M3 or a Pirelli Sottozero; a highway use and good handling bias basically for non-snow/ice conditions. When you look in the A8 sizes, and especially in the 27.6" tire circumference group, your choices are pretty limited. Thus if you have a strong preference toward a particular model/type of snow tire, you may find it sends you toward a certain diameter wheel to get that tire you really want. Said another way, choices are limited in the A8's particular tire circumference. By contrast, in the A6 25" circumference, there are lots of choices in most all the brands/models. Unfortunately the sites like Tire Rack (or anybody else) don't have any search capability by circumference, so you need to go to the specs page for each tire you are thinking about and look it up.

Finally, lay on top of this width, which again given limited A8 choices may force you to a particular diameter. In my case, when I most need the benefits of snow tires, I put a premum on stopping on ice on local roads and not sliding on the same in local driving. That's the scariest thing I encounter in winter Tahoe driving, and most of the time why I see the "city folk" SUV's, Jeeps and Volvo XC90's in ditches, upside down and crunched into phone poles and trees, or occasionally the 4x4 pickup spinning out right around me. I've encountered every one of those (and those vehicles) multiple times as a reference point. Despite the TV ad footage and mental images, you rarely have the chance to be the Quattro road warrior cutting through crud at some speed with no one on the road; instead ill equipped SUVs and wannabe AWD's with city slicker tires are the norm and traffic is slowed. To me, that nets to wide is just fine for that extra stop traction on glare surfaces, and the benefits of narrower widths to cut through crud and avoid the floaty (not hydroplaning) feeling you can get at times in a wider width rarely comes into play.

I'm still looking for the right wheels (I prefer OEM), but my guess is I either settle for 18's with a 245/50 (gets me 27.7" in a Dunlop M3, and I really like that tire from A6 use in a 255), or I stay at 20's in a Pirelli Sottozero (which are currently out of stock at Tire Rack in the 275's and the 265's take me back down to 27"). I didn't put it in my title, but if common sense sticks with me and I don't really need that high cornering ability Dec. to March, then the 245's are my smarter choice...because of...tread noise. Relative to the summers I have used (Dunlops generally, sometimes Pirellis), snows are clearly noiser at highway speeds, even in a highway model like a Dunlop M3. Pulling down the width helps counteract that.

Hopefully by laying out my thinking on the variables, you could pick the ones that matter to you. Thus, if I were in Chicago or Michigan I would probably put a lot of weight on the sidewall protection, and right away go to the smaller wheels. If I were cutting through crud every day on the way home on a secondary road or interstate, I would go narrower, etc.

Good luck.

MP4.2+6.0

See my dissertation above on the variables

tcr20

when I do the searches. PS: Tahoe in the summer is my favorite place in the world! I go at least once or twice a summer, and I want to live there someday!!! Don't usually see many Audi's, up there, especially A8's but I saw one this past summer. Mostly an SUV and Subaru crowd from what I can see, even in the summer, surprisingly enough.

MP4.2+6.0

Locals tend to own Subie's disprotionately. But they are lost in the sea of 80%+ SUV's in winter. And if it's an XC90, X5 or occasional ML or Q7, as well as all Infiniti's, Lexi and most Acuras, it screams Bay Area flatlander. You do see A6's and A4's; owner of Mountain Hardware in Truckee I think may have an A8. BMW sedans that come out in summer vaporize in winter, except for the occasional college kid with an old 320i or something, or clueless city dweller. Their AWD's are changing it a bit, but Audi sedans outnumber any other Euro sedan by a good margin.

A8 probably won't see snow or snow tires this year (going up tonight though); the 7 year old 4.2 can take the beating on the paint another season while the black A8 stays clean... Or the Toyota Sienna AWD with snows...the practical choice.

Silver Streakin'

smallest tire patch possible = pushes down harder per square inch = better for snow/slush